A sequence of nested (daily) trials are emulated with increasing time (t1, t2, …, tn), iterating over the days in the enrollment period. At each eligible time during the enrollment period, the vaccination status of eligible individuals is assessed and every individual who has completed a primary vaccination schedule at that time (coded here as initiation of the intervention strategy when emulating a nested target trial) is matched to an individual who has not (yet) completed the primary vaccination schedule (coded here as the control strategy when emulating a nested target trial). Newly vaccinated individuals (completing a primary vaccination schedule) are eligible for inclusion in the study, even if they had previously been selected in the “no (or partial) vaccine group”. Vaccinations have been administered in the context of national public health programs, without interference/manipulation of the research subjects.
We assess the covariate balance, which is the extent to which the distribution of covariates is similar across the intervention groups.
Standardized Mean Differences
The Standardized Mean Difference (SMD) represents a standardized difference in mean between contrasted intervention groups for each covariate.
| Means intervention group | Means control group | Standardized mean difference | |
|---|---|---|---|
| distance | 0.898848438 | 0.895000673 | 0.2045432558 |
| sex_cd0 | 0.017416364 | 0.009977827 | 0.0568622458 |
| sex_cd1 | 0.473374264 | 0.506651885 | -0.0666498088 |
| sex_cd2 | 0.509209372 | 0.483370288 | 0.0516869362 |
| age_cd10 | 0.117027941 | 0.119733925 | -0.0084179597 |
| age_cd11 | 0.129933592 | 0.124168514 | 0.0171462146 |
| age_cd12 | 0.127928831 | 0.143015521 | -0.0451683046 |
| age_cd13 | 0.111514848 | 0.096452328 | 0.0478526717 |
| age_cd14 | 0.096604436 | 0.087583149 | 0.0305373248 |
| age_cd15 | 0.068287182 | 0.073170732 | -0.0193608748 |
| age_cd16 | 0.044480642 | 0.046563193 | -0.0101016068 |
| age_cd17 | 0.026061897 | 0.017738359 | 0.0522443422 |
| age_cd18 | 0.023180053 | 0.023281596 | -0.0006748217 |
| age_cd2 | 0.001754166 | 0.001108647 | 0.0154260491 |
| age_cd3 | 0.002380654 | 0.000000000 | 0.0488501289 |
| age_cd4 | 0.007267260 | 0.005543237 | 0.0202974469 |
| age_cd5 | 0.013156246 | 0.011086475 | 0.0181648672 |
| age_cd6 | 0.027064278 | 0.021064302 | 0.0369750888 |
| age_cd7 | 0.044480642 | 0.042128603 | 0.0114087784 |
| age_cd8 | 0.063400576 | 0.078713969 | -0.0628416921 |
| age_cd9 | 0.095476757 | 0.108647450 | -0.0448177371 |
| residence_area_cd731 | 0.155870192 | 0.146341463 | 0.0262693175 |
| residence_area_cd732 | 0.149855908 | 0.154101996 | -0.0118961317 |
| residence_area_cd733 | 0.694273901 | 0.699556541 | -0.0114661965 |
| pregnancy_blTRUE | 0.025435409 | 0.036585366 | -0.0708187905 |
| institutionalized_blTRUE | 0.036837489 | 0.028824834 | 0.0425384506 |
| foreign_blTRUE | 0.148227039 | 0.137472284 | 0.0302673847 |
| socecon_lvl_cd1 | 0.022678862 | 0.018847007 | 0.0257383002 |
| socecon_lvl_cd2 | 0.137702042 | 0.118625277 | 0.0553612471 |
| socecon_lvl_cd3 | 0.360481143 | 0.375831486 | -0.0319705515 |
| socecon_lvl_cd4 | 0.344067160 | 0.338137472 | 0.0124818939 |
| socecon_lvl_cd5 | 0.135070793 | 0.148558758 | -0.0394616672 |
| comorbidities_blTRUE | 0.501190327 | 0.483370288 | 0.0356401786 |
| immunestatus_blTRUE | 0.275654680 | 0.276053215 | -0.0008918898 |
| Means intervention group | Means control group | Standardized mean difference | |
|---|---|---|---|
| distance | 0.504282811 | 0.4957171893 | 0.166817773 |
| sex_cd0 | 0.017532551 | 0.0090241073 | 0.064828877 |
| sex_cd1 | 0.472218641 | 0.4964548150 | -0.048547344 |
| sex_cd2 | 0.510248808 | 0.4945210777 | 0.031462070 |
| age_cd10 | 0.116668815 | 0.1303338920 | -0.042566986 |
| age_cd11 | 0.130978471 | 0.1387134201 | -0.022926736 |
| age_cd12 | 0.127884491 | 0.1361351038 | -0.024705306 |
| age_cd13 | 0.111512183 | 0.1125435091 | -0.003276493 |
| age_cd14 | 0.095784453 | 0.0960422844 | -0.000876098 |
| age_cd15 | 0.068067552 | 0.0666494779 | 0.005630366 |
| age_cd16 | 0.044862705 | 0.0417687250 | 0.014946580 |
| age_cd17 | 0.025654248 | 0.0197241201 | 0.037508340 |
| age_cd18 | 0.023075931 | 0.0193373727 | 0.024899704 |
| age_cd2 | 0.001804821 | 0.0005156633 | 0.030372557 |
| age_cd3 | 0.002449401 | 0.0012891582 | 0.023472068 |
| age_cd4 | 0.007219286 | 0.0043831378 | 0.033500794 |
| age_cd5 | 0.013149413 | 0.0092819389 | 0.033950687 |
| age_cd6 | 0.027201238 | 0.0212711100 | 0.036455092 |
| age_cd7 | 0.044347041 | 0.0407373985 | 0.017534033 |
| age_cd8 | 0.063684414 | 0.0643289932 | -0.002639663 |
| age_cd9 | 0.095655537 | 0.0969446951 | -0.004383129 |
| residence_area_cd731 | 0.156117056 | 0.1486399381 | 0.020600033 |
| residence_area_cd732 | 0.150058012 | 0.1459327059 | 0.011551329 |
| residence_area_cd733 | 0.693824932 | 0.7054273559 | -0.025173225 |
| pregnancy_blTRUE | 0.025009669 | 0.0192084569 | 0.037150494 |
| institutionalized_blTRUE | 0.037643419 | 0.0313265438 | 0.033188662 |
| foreign_blTRUE | 0.148768854 | 0.1414206523 | 0.020649108 |
| socecon_lvl_cd1 | 0.022560268 | 0.0105710971 | 0.080736893 |
| socecon_lvl_cd2 | 0.137811009 | 0.1336857032 | 0.011967763 |
| socecon_lvl_cd3 | 0.359804048 | 0.3765631043 | -0.034918862 |
| socecon_lvl_cd4 | 0.345752224 | 0.3560654892 | -0.021684159 |
| socecon_lvl_cd5 | 0.134072451 | 0.1231146062 | 0.032159892 |
| comorbidities_blTRUE | 0.501095784 | 0.5016114477 | -0.001031329 |
| immunestatus_blTRUE | 0.277684672 | 0.2776846719 | 0.000000000 |